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uu Decode function

john

function decode64(input) {

var keyStr = "ABCDEFGHIJKLMNOP" +
"QRSTUVWXYZabcdef" +
"ghijklmnopqrstuv" +
"wxyz0123456789+/" +
"=";

var output = "";

var chr1, chr2, chr3 = "";

var enc1, enc2, enc3, enc4 = "";

var i = 0;

// remove all characters that are not A-Z, a-z, 0-9, +, /, or =

var base64test = /[^A-Za-z0-9\+\/\=]/g;

if (base64test.exec(input)) {

alert("There were invalid base64 characters in the input text.\n" +

"Valid base64 characters are A-Z, a-z, 0-9, '+', '/',and '='\n" +

"Expect errors in decoding.");

}

input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");

do {

enc1 = keyStr.indexOf(input.charAt(i++));

enc2 = keyStr.indexOf(input.charAt(i++));

enc3 = keyStr.indexOf(input.charAt(i++));

enc4 = keyStr.indexOf(input.charAt(i++));

chr1 = (enc1 << 2) | (enc2 >> 4);

chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);

chr3 = ((enc3 & 3) << 6) | enc4;

output = output + String.fromCharCode(chr1);

if (enc3 != 64) {

output = output + String.fromCharCode(chr2);

}

if (enc4 != 64) {

output = output + String.fromCharCode(chr3);

}

chr1 = chr2 = chr3 = "";

enc1 = enc2 = enc3 = enc4 = "";

 

} while (i < input.length);
return decodeURI(output);

}

 

source:
http://ntt.cc/2008/01/19/base64-encoder-decoder-with-javascript.html